One of the problems encountered with injection blow molding apparatus is that injection molds are damaged by core rods which have hardened residue on them when they are returned to the injection station. As a precaution, it is common practice to have means located between the pick-off station and the injection station for detecting any residue which may be left on a core rod.
Large injection blow molding machines have a plurality of core rods extending from different faces of an indexing head, and these core rods extend from a flat side face of the indexing head and are presented to each station simultaneously as the indexing head turns intermittently during the operation of the machine. Because of the fact that the core rods extend from a flat face on the side of the indexing head, they do not all travel through the same arc when moving from the pick-off station to the injection station. A rod at the center of the face is closer to the axis of rotation of the indexing head and therefore moves about a shorter radius than other rods which are located toward the opposite ends of the side face of the head and which are substantially further from the center of rotation.
Residue detecting apparatus has been used with cams for shifting the position of the core rod detector to coincide with the path of movement of successive core rods; but such cam-operated mechanism is very complicated, and the cam must be especially designed for the conditions under which it is to be used.
When using longer core rods, or substantially shaped core rods and/or core rods mounted further apart, individual cam followers for each different core rod set would have to be installed. Fast rotating indexing heads of modern machines may override detecting devices located between pick-off and injection stations. Also, such detecting devices, located between stations, cannot be used with machines in which the indexing heads are built to rotate prior to reaching their upper positions to achieve fast indexing speeds.
This invention provides a traversing core rod detecting device which is universally adaptable to all core rod shapes, lengths and mounting widths by adjusting threaded parts up or down so that their lower ends correspond to the longitudinal contour of the outside surface of each core rod.
As soon as blown containers or other articles have been stripped from the core rods at the pick-off station, the pick-off plate remains in its foremost position for several seconds; and during this period, the detecting device travels across all of the core rods successively. If any unstripped plastic is detected, the part of the detecting apparatus which contacts with the unstripped residue imparts an angular movement to the detecting apparatus and operates a micro-switch, or other device, which stops the machine until the residue can be removed from the core rod.
The residue detector is supported by a carriage which runs along a track and its motion is preferably tied in with the programming apparatus that operates the injection blow molding machine.
In the preferred embodiment of the invention, the parts of the detector which strike against residue on the core rods are preferably Nylon rods threaded to a support by which they are carried; and these rods are threaded so that they can be turned one way or the other in order to bring the ends of the rods to the necessary location adjacent to the part of a core rod across which each particular rod passes during a traverse of the detector.
Other objects, features and advantages of the invention will appear or be pointed out as the description proceeds.